Method and apparatus for manipulating a sample

ABSTRACT

A method and apparatus for manipulating the surface of a sample including a cantilever, a first tip mounted on the cantilever, and a second tip mounted on the cantilever, the first and the second tip being configured to combine to form an imaging probe and to separate to form a manipulation probe. The first and second tips are configured to form a first position characterized in that the tips combine to form an imaging tip and the first and the second tip are configured to form a second position characterized in that the tips separate to manipulate particles on a surface of a sample. The tips can be configured to form the first position when a voltage is applied across the tips, and preferable extend downwardly from the cantilever substantially perpendicular thereto.

This application is a continuation-in-part of U.S. application Ser. No.09/855,960, filed May 15, 2001 now U.S. Pat. No. 6,530,268, titledApparatus and Method for Isolating and Measuring Movement in MetrologyApparatus, which is a continuation-in-part of U.S. application Ser. No.09/803,268, filed Mar. 9, 2001 now U.S. Pat. No. 6,612,160.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention is directed to scanning probe microscopy. Moreparticularly, the present invention is directed to a method andapparatus for characterizing and manipulating a sample.

2. Description of Related Art

Presently, scanning probe microscopes (SPMs) are typically used todetermine the surface characteristics of a sample, commonly biologicalor semiconductor samples, to a high degree of accuracy, down to theAngstrom scale. An SPM operates by scanning a measuring probe assemblyhaving a sharp stylus over a sample surface while measuring one or moreproperties of the surface. One example of an SPM is an atomic forcemicroscope (AFM) wherein a measuring probe assembly includes a sharpstylus attached to a flexible cantilever. Commonly, an actuator such asa piezoelectric tube, often referred to as a piezo tube, is used togenerate relative motion between the measuring probe and the samplesurface. A piezoelectric tube moves in one or more directions whenvoltages are applied to electrodes disposed inside and outside the tube.

In the operation of an AFM, preferably, a measuring probe assembly isattached to a piezoelectric tube actuator so that the probe may bescanned over a sample fixed to a support. According to an alternativemethod, the probe assembly is held in place and the sample, which iscoupled to a piezoelectric tube actuator, is scanned under it. In bothAFM examples, the deflection of the cantilever is measured by reflectinga laser beam off the backside of the cantilever and towards a positionsensitive detector.

In a contact mode or deflection mode of AFM operation, the AFM operatesby placing the tip at the end of the cantilever of the probe directly ona sample surface so that the cantilever obtains a preset deflection.Preferably, the force between the tip and the sample surface is selectedby the user, and defines an operating point of the AFM, the deflectionsetpoint. When scanning the surface laterally, the response of thecantilever to variations in the surface is monitored by an AFMdeflection detection system and can be used to create an image of thesample surface. As suggested previously, a typical deflection detectionsystem employed in AFM is an optical beam system that opticallydetermines the deflection of the cantilever by light reflected off thecantilever onto a detector. Often, the height from the surface of thesample to a fixed end of the cantilever is adjusted with feedbacksignals that operate to maintain a predetermined amount of cantileverdeflection (i.e., generally at the deflection setpoint) during scanning.A reference signal is often applied to one input of a feedback loop ofan AFM system. The output of the feedback loop is then applied as anadjustment signal to an actuator to maintain constant cantileverreaction and maintain relative height. An image of the surface is thencreated by monitoring the feedback signals and plotting the adjustmentamount versus lateral position of the cantilever tip.

In TappingMode™ (which is a trademark of Veeco Instruments, Inc.), aprobe tip makes contact with a sample as it taps across the surface ofthe sample. An AFM employing TappingMode™ uses oscillation of acantilever to reduce the forces on the sample. In particular, a specificcantilever is oscillated near or at its resonant frequency. A feedbackloop is used to maintain a desired amplitude of oscillation. Thefeedback circuit adjusts a vertical position of the cantilever or thesample to maintain the desired amplitude as the cantilever traverses thesurface of the sample. The signals used to adjust the vertical positionare used to create an image of the surface versus the lateral positionof the cantilever tip.

Unfortunately, present SPMs do not provide an adequate mechanism formanipulating the sample being imaged. For example, present SPMs do notadequately provide for accurately picking up, nudging, etc. the sampleor portions thereof. Manipulation of the sample can be difficult becausepresent SPMs do not allow for performing action on what often times arenanoscale objects. Present SPMs typically use the same probe tomanipulate and image or they use one probe to manipulate and one probeto image but the design is such that there is a large horizontaldistance between the manipulating and the imaging probes. This cancreate inaccuracies in determining the location of the manipulationprobe with respect to an imaging probe because inaccuracies in offsetdeterminations and inaccuracies in the precision of moving the probes.This offset can result in errors when attempting to manipulate thesample. Furthermore, present SPMs do not provide for adequate accuracyin manipulating particles on a sample due to limitations in the controlaccuracy of the actuator of the SPM. Another difficulty is that presentSPMs encounter drift in the relative positions of the tip and sample,which can result in a probe manipulating an incorrect position on thesample. Therefore, an SPM that overcomes these drawbacks was desired.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for manipulatingthe surface of a sample. In particular, the present invention overcomesthe above mentioned drawbacks and provides additional benefits byproviding probes that can perform both imaging and manipulatingfunctions on a sample or can be controlled independently to image withone probe and manipulate with other probe without compromising accuracy.The function of the probes include imaging with one probe while theother probe is held above the sample surface which is used formanipulation. This mechanism protects the imaging probe from beingcontaminated during manipulation. Other manipulation functions includenanotweezing functions that are performed with a tip that can be openedand closed to pick up, move, and drop objects on a sample. The tip canalso cut objects on a sample and provide electrostatic forces to asample. The tip is perpendicular to a cantilever. Thus, the tip can beclosed to perform imaging functions on the sample. Thus, the tip isextremely accurate because the imaging tip is the same tip as themanipulation tip.

According to one embodiment, the present invention provides a scanningprobe microscope including a cantilever, a first tip mounted on thecantilever, and a second tip mounted on the cantilever, the first andthe second tip being configured to combine to form an imaging tip and toseparate to form a manipulation tip. The first and the second tip areconfigured to form a first position characterized in that the tipscombine to form an imaging tip and the first and the second tip areconfigured to form a second position characterized in that the tipsseparate to manipulate particles on a surface of a sample. The tips canbe configured to form the first position when a voltage is appliedacross the tips.

The scanning probe microscope can include a first electrode coupled tothe first tip and a second electrode coupled to the second tip. The tipscan be configured to form the first position when a voltage is appliedacross the first electrode and the second electrode. The cantilever caninclude a first cantilever portion, where the first tip is mounted onthe first cantilever portion and a second cantilever portion, where thesecond tip is mounted on the second cantilever portion.

The scanning probe microscope can also include a first electrode coupledto the first cantilever portion and a second electrode coupled to thesecond cantilever portion. The tips can be configured to form the firstposition when a voltage is applied across the first electrode and thesecond electrode.

According to another embodiment, the present invention provides ascanning probe microscope including a cantilever having a longitudinalaxis, a first tip mounted on the cantilever substantially perpendicularto the longitudinal axis, and a second tip mounted on the cantileversubstantially perpendicular to the longitudinal axis. The cantilever caninclude a first cantilever portion, where the first tip is mounted onthe first cantilever portion and a second cantilever portion, where thesecond tip is mounted on the second cantilever portion.

The scanning probe microscope can also include a first electrode coupledto the first cantilever portion and a second electrode coupled to thesecond cantilever portion. The tips can be configured to combine byapplying a voltage across the first electrode and the second electrode.The tips can be configured to combine to scan a surface of a sample tocreate an image of the surface of the sample. The tips can further beconfigured to combine by applying a voltage across the first tip and thesecond tip. The tips can also be configured to combine by applying avoltage across the first cantilever portion and the second cantileverportion. The scanning probe microscope can additionally include a firstelectrode coupled to the first tip and a second electrode coupled to thesecond tip. The tips can be configured to combine by applying a voltageacross the first electrode and the second electrode.

According to another embodiment, the present invention provides ananomechanical tweezing apparatus including a cantilever having a firstcantilever portion and a second cantilever portion, a first tip coupledto the first cantilever portion, a second tip coupled to the secondcantilever portion, a first electrode coupled to the first cantileverportion, and a second electrode coupled to the second cantileverportion. The first cantilever portion and the second cantilever portionare configured so that the first tip and the second tip squeeze intocontact when a sufficient voltage is applied across the first electrodeand the second electrode. The first tip and the second tip are alsoconfigured to grip microscopic material. The first tip and the secondtip are additionally configured to form a single imaging stylus whenthey are squeezed into contact. The first tip can be coupledsubstantially perpendicular to a longitudinal axis of the firstcantilever portion and the second tip can be coupled substantiallyperpendicular to a longitudinal axis of the second cantilever portion.

According to another embodiment, the present invention provides methodfor interacting with a surface of a sample and switching between imagingmodes by including the following process: Turning off the feedback ofthe probe, lifting the probe from the surface, storing a change indeflection or amplitude between a deflection or amplitude setpoint and afree air deflection or amplitude, and turning on the feedback. Themethod can also include switching between TappingMode™ and contact modeor the reverse by turning off feedback of the probe, setting adeflection setpoint based on a free air deflection or amplitude combinedwith the change in deflection or amplitude, changing the input to thefeedback loop and turning on the feedback. The method can includemanipulating the surface with the probe. The probe can include acantilever, a first tip mounted on the cantilever, and a second tipmounted on the cantilever, the first and the second tip being configuredto combine to form an imaging tip. The method can also include applyinga voltage across the first tip and the second tip to combine the firsttip and the second tip to form an imaging tip. The method can alsoinclude applying a voltage across the first tip and the second tip tocombine the first tip and the second tip to form an imaging tip.

According to another embodiment, the present invention provides methodfor operating a probe that interacts with a surface of a sampleincluding scanning a region the surface of the sample with the probe,manipulating the surface of the sample with the probe, and rescanning asubregion of the region of the surface of the sample. The manipulatingstep can further include manipulating the surface of the sample with aprobe other than the probe used to scan the region of the surface of thesample. The manipulating step can also include manipulating the surfaceof the sample with the probe used to scan the region of the surface ofthe sample. The manipulating step can additionally include manipulatinga subregion of the region of the surface of the sample with the probe,and the rescanning step can include rescanning the manipulated subregionof the region of the surface of the sample.

The manipulating step can include manipulating particles on the surfaceof the sample with the probe. The manipulating step can includemanipulating particles on the surface of the sample by picking up theparticles with the probe. The probe can include a cantilever, a firsttip mounted on the cantilever, and a second tip mounted on thecantilever, the first and the second tip being configured to combine toform an imaging tip. The method can also include applying a voltageacross the first tip and the second tip to combine the first tip and thesecond tip to form an imaging tip.

According to another embodiment, the present invention provides a methodfor interacting with a surface of a sample including scanning thesurface of the sample with a probe to create a first image, scanning thesurface of the sample with a probe to create a second image, anddetermining a relative position of the probe by comparing the firstimage to the second image. The method can include continuously adjustinga position of the probe based on a result obtained from the determiningstep for subsequent manipulation and imaging steps.

The probe can include a cantilever, a first tip mounted on thecantilever, and a second tip mounted on the cantilever, the first andthe second tip being configured to combine to form an imaging tip. Themethod can include applying a voltage across the first tip and thesecond tip to combine the first tip and the second tip to form animaging tip.

According to another embodiment, the present invention provides a methodfor interacting with a surface of a sample, including scanning thesurface of the sample with a probe to create an image, performingpattern recognition on the image to obtain a pattern recognized image,and automatically manipulating the surface of the sample with the probebased on the pattern recognized image. The probe can include acantilever, a first tip mounted on the cantilever, and a second tipmounted on the cantilever, the first and the second tip being configuredto combine to form an imaging tip. The method can include applying avoltage across the first tip and the second tip to combine the first tipand the second tip to form an imaging tip.

According to another embodiment, the present invention provides a methodof making a nanomechanical tweezing apparatus including forming a probehaving a tip coupled to a cantilever, the probe having a longitudinalaxis, and performing milling along a longitudinal axis of the probe toseparate the probe into a first cantilever including a first tip and asecond cantilever including a second tip. The performing step canperform focused ion beam milling along the longitudinal axis of theprobe to separate the probe into a first cantilever including a firsttip and a second cantilever including a second tip. The method caninclude coupling a first electrode to the first cantilever portion, andcoupling a second electrode to the second cantilever portion. The probecan include a combination of silicon and silicon dioxide. The method canalso include performing metal deposition on a surface of the probe.

According to another embodiment, the present invention provides a methodof making a probe for a scanning probe microscope including forming afirst cantilever portion, forming a second cantilever portionsubstantially parallel to the first cantilever portion, forming a firsttip portion on the first cantilever portion substantially perpendicularto the first cantilever portion, and forming a second tip portion on thesecond cantilever portion substantially perpendicular to the secondcantilever portion. The method can include coupling a first electrode tothe first cantilever portion, and coupling a second electrode to thesecond cantilever portion. The method can also include forming a layerof insulation on the cantilever portion and forming a layer of aconductive material on a surface of the cantilever portion. Thecantilever can include silicon, the layer of insulation can includesilicon oxide or silicon dioxide, and the layer of conductive materialcan include metal.

According to another embodiment, the present invention provides a methodof making a probe for a scanning probe microscope including forming aprobe that contains a U-shaped cantilever with a tip integrated on eachof the arms. The arms contain a layer that actuates the desired tip toengage the surface while the other tip remains above the surface. Theactuation layer can include a piezoelectric material such as ZnO or athermal resistance layer formed out of polycrystalline silicon orimplanted silicon layers. The actuation process can be achieved byapplying a potential to the piezoelectric material or by heating thethermal element. The actuated arm will shape in the form of bow makingthe tip touch the surface while other tip remains above the surface.This mechanism will facilitate the imaging and manipulation of sampleswith different tips.

According to another embodiment, the present invention provides a methodof making a probe for a scanning probe microscope including forming twocantilevers with integrated tips at the free ends of them and separatedfrom each other vertically when the probe is mounted in the apparatus.The cantilevers are separated with an insulator layer and have a metallayer coated on both the cantilevers. The cantilevers can be made out ofsilicon as well as that of silicon dioxide. The cantilevers can be madeto move towards or away from each other by applying a suitableelectrostatic force. This movement of the cantilevers in a verticalplane facilitates use of one probe for imaging and the other forcarrying out another function such as manipulation.

U.S. application Ser. No. 09/855,960, filed May 15, 2001, discloses anApparatus and Method for Isolating and Measuring Movement in MetrologyApparatus and is incorporated by reference in its entirety. Inparticular, according to another embodiment, the present applicationprovides an assembly including an actuator with a longitudinal axishaving a fixed end, and a free end configured to translate in at leastone direction with respect to the fixed end, a multiple bar linkagehaving first and second links mutually constrained to translate withrespect to each other, and wherein the first link is fixed to areference structure and the second link is constrained to translate in adirection generally parallel to the longitudinal axis of the actuator, acoupling having first and second ends, the first end being fixed to theactuator proximate to its free end, and the second end being fixed tothe second link, the coupling adapted to transmit displacement in adirection substantially parallel to the longitudinal axis of theactuator, an objective fixed to the reference structure, wherein theobjective is between a light source and a position sensor, and theposition sensor measures displacement of the objective in at least onedirection generally perpendicular to the longitudinal axis of theactuator, and a probe coupled to the actuator, wherein the probe isconfigured to manipulate the surface of a sample.

The light source and the position sensor can be stationary. Theobjective can include a set of microlenses. The set of microlenses canprovide optical magnification to increase a signal-to-noise ratio. Themagnification can be M=1+i/o where i is an orthogonal distance from theprincipal plane of the set of microlenses to the position sensor and ois an orthogonal distance from the principal plane of the set ofmicrolenses to the light source. Movement of a beam of electromagneticradiation from the light source directed to the position sensor throughthe set of microlenses can be multiplied by a factor of M. The assemblycan be a scanning probe microscope. Also, the actuator can be apiezoelectric or electrostrictive actuator The probe can include acantilever, a first tip mounted on the cantilever, and a second tipmounted on the cantilever, the first and the second tip being configuredto combine to form an imaging tip. A voltage can be applied across thefirst tip and the second tip to combine the first tip and the second tipto form an imaging tip.

Accordingly, the present invention provides for the accuratemanipulation of particles, objects, surfaces, and the like on a sample.Also, the present invention can accurately pick up, move, and depositparticles on the sample. In particular, the present invention can act asa nanomechanical tweezers that provides for manipulating the surface andother similar aspects of a sample. The present invention also allowsmanipulatation of a sample with one probe and imaging with anotherprobe, both attached to the same substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the present invention will be describedwith reference to the following figures wherein like numerals designatelike elements, and wherein:

FIG. 1 is an exemplary illustration of a probe according to onepreferred embodiment;

FIG. 2 is an exemplary illustration of the first tip and the second tipof the tip of the probe in a first position according to one embodiment;

FIG. 3 is an exemplary illustration of the first tip and the second tipof the tip of the probe in a second position according to oneembodiment;

FIG. 4 is an exemplary illustration of a system for scanning the surfaceof a sample according to one embodiment;

FIG. 5 is an exemplary illustration of a probe according to anotherembodiment;

FIG. 6 is an exemplary illustration of a probe according to anotherembodiment;

FIGS. 7-20 are exemplary illustrations of a process for manufacturing aprobe according to one embodiment;

FIGS. 21-22 are exemplary illustrations of a probe system forimplementation of a focused ion beam milling technique for manufacturingthe probe according to one embodiment;

FIGS. 23-33 are exemplary illustrations of a process for manufacturing aprobe according to one embodiment;

FIG. 34 is an exemplary illustration of a user interface for use withthe probe according to one embodiment;

FIG. 35 is an exemplary illustration of a scanning probe microscopesystem according to one embodiment;

FIG. 36A is an exemplary illustration of a scanning probe microscopesystem according to various embodiments;

FIG. 36B is a side elevation cross-sectional view of the piezoelectricactuator assembly including an optical measuring apparatus according toa preferred embodiment of the present invention;

FIGS. 36C-36D are exemplary illustrations of alternate embodiments ofthe optical measuring apparatus shown in FIG. 36B;

FIG. 37 is an exemplary illustration of control circuitry for a scanningprobe microscope system according to one embodiment;

FIG. 38 is an exemplary flowchart outlining the operation of switchingbetween a deflection mode and an amplitude mode according to a oneembodiment;

FIG. 39 is an exemplary flowchart outlining the operation of switchingbetween an amplitude mode and a deflection mode according to oneembodiment;

FIG. 40 is a schematic side-elevational view of an apparatus for forminga tip configured for manipulation of a sample, according to an alternateembodiment;

FIG. 41 is a schematic plan view of the tip formed using the apparatusshown in FIG. 40;

FIG. 42 is an exemplary illustration of a probe system according to analternate embodiment;

FIG. 43 is an exemplary illustration of a probe system according to analternate embodiment; and

FIG. 44 is an SEM photograph of an exemplary probe fabricated accordingto an alternate embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is an exemplary illustration of a probe 100 particularly adaptedfor both imaging and manipulating samples, such as biological samples,(e.g., DNA) according to one embodiment. The probe 100 can include acantilever 140 and a tip or tweezers 110 mounted substantiallyperpendicular to the cantilever 140. The tip 110 can include a first tipor prong 120 and a second tip or prong 130 mounted substantiallyperpendicular to the cantilever. The cantilever 140 can be mounted to abase 190 and can have a longitudinal axis running from the end of thecantilever mounted to the base to the opposite, free end of thecantilever. Preferably, the tips 120 and 130 can be mountedsubstantially perpendicular to the longitudinal axis of the cantilever.The cantilever 140 can include a first cantilever portion 150, and asecond cantilever portion 160 disposed generally parallel thereto. Afirst electrode 170 and a second electrode 180 can be coupled to thetips 120 and 130 or the cantilevers 150 and 160.

In operation, the probe 100 can be used to image, measure, and/ormanipulate a sample. In particular, an electrical potential can beapplied to the first and second electrodes 170, 180, respectively, tocombine the tips 120 and 130 so that together they simulate a tip of aconventional scanning probe microscope to obtain an image or measurementof the surface of the sample using known microscopy techniques.Additionally, the tips can be combined using techniques such as thermalactuation, actuation using piezoelectric elements, or any othertechnique useful for adjusting the position of a probe. For example, theprobe can include a layer of aluminum, platinum, alloy, isopolysilicon,boron, or the like. The electric potential can be opposite polaritiesbetween the tips, like polarities between the tips, one voltage and oneground potential applied to each tip, or any useful potential forcombining or separating the tips. These tip operation techniques can beapplied to the tips and probes of all of the disclosed embodiments.

When together, tips 120, 130 can be used for nanomanipulation of sampleparticles, such as “nudging” them, etc. Additionally, the tips 120 and130 can be opened and closed by applying appropriate voltages to thefirst electrode 170 and the second electrode 180 to act as ananomechanical tweezers. For example, a zero voltage can be applied toopen the tip 110 and non-zero voltage can be applied to close the tip110. Thus, the tip 110 can then be used to pick up particles, replaceparticles, place particles, move particles, remove particles, applyvoltages, and perform other manipulations on a sample. The tip 110 canfurther be used for dip pen or other lithography. For example, the tip110 can be used to remove or alter material in a thin layer or in ahomogeneous layer of a sample. Furthermore, the tips 120 and 130 can beseparated and positioned on a such that both tips are in contact withthe sample. Then both tips 120 and 130 can be used to measure localconductivity or other electrical properties on the surface of the sampleor of the feature manipulated. Furthermore, additional tips may beemployed to facilitate, for example, a robotic hand, an array of probes,or the like. All of these techniques can be applied to the probesdisclosed in all of the embodiments.

In this regard, the probe 100 can be used to manipulate or cut DNA orother particles. The probe 100 can further be used to manipulateparticles across the surface of a sample to create different structureson the sample. For example, the probe 100 can be used to manipulateconductive particles to create structures with specific electricalproperties. The probe 100 can also be used for lithography by dippinginto and placing fluid with specific photolithographic properties on asample. The probe 100 can additionally be used to study electricalparameters. For example, the tips 120 and 130 can be opened a specificdistance and a voltage can be applied across the tips. Additionally, asecond probe (e.g., a conventional AFM probe) can be used to performimaging of a sample, while the probe 100 can be used to manipulate thesample. For example, the second probe can be placed a few microns fromthe probe 100 to perform imaging of a sample while the probe 100manipulates the sample. An offset can be applied to accurately accountfor the displacement between the two probes. Also, one probe can raiseor lower relative to the other probe to alternate image and manipulatethe sample.

Force feedback can be used to inform an operator of when the probe 100encounters particles or irregularities in the surface of the sample. Forexample, such feedback can be used to cause the operator to feelphysical resistance on an input device such as a joystick when the probe100 encounters a particle on the surface of the sample.

Also, the probe 100 can be used with any mode of scan probe imagingincluding contact atomic force microscopy (AFM), non-contact AFM,lateral force microscopy (LFM), scanning tunneling microscopy (STM),magnetic force microscopy (MFM), scanning capacitance microscopy (SCM),force modulation microscopy (FMM), phase imaging, electrostatic forcemicroscopy (EFM), and other modes of operating a scanning probemicroscope. For example, lateral force microscopy (LFM) could be used toimage the sample by monitoring the torsional response of the probe and,as with AFM, using that data to locate the regions of interest for latermanipulation.

FIG. 2 is an exemplary illustration of the first tip 120 and the secondtip 130 of the tip 110 of the probe 100 in a first position according toone embodiment. To achieve the first position, for example, a voltage isapplied across the electrodes 170 and 180. Thus, the first tip 120 andthe second tip 130 combine to form an imaging tip. Therefore, the tip110 can be used to obtain an image of a surface of a sample. This imageof the surface of a sample can include properties such as the physicalcharacteristics of the sample, the electrical characteristics of thesample, electromagnetic characteristics of the sample, characteristicsbelow the surface of the sample, or any other characteristic of thesample.

FIG. 3 is an exemplary illustration of the first tip 120 and the secondtip 130 of the tip 110 of the probe 100 in a second position accordingto one embodiment. To achieve the second position, for example, a groundvoltage is applied across the electrodes 170 and 180. Thus, the firsttip 120 and the second tip 130 are configured to form a tweezers tip 110capable of manipulating particles on a surface of a sample. Inoperation, a suitable voltage is applied across the electrodes 170 and180 to open and close the tweezers tip 110 to manipulate particles on asurface of a sample as described above.

FIG. 4 is an exemplary illustration of a system 400 for scanning thesurface of a sample 410 according to one embodiment. The system 400includes the probe 100, a sample 410, a probe mount or actuator 420, asample mount or actuator 430, and a controller 440. In operation, theprobe 100 is scanned across the surface of the sample 410. This scanningis performed either by moving the probe 100 relative to the sample 410,the sample 410 relative to the probe 100, or a combination of eachrelative to each other. This scanning is performed by applying voltagesto the actuators 420 and 430, or by other techniques of adjusting theposition of the probe 100 and the sample 410. When in a first position,the probe 100 can obtain an image of the surface of the sample 410including different characteristics of the sample 410, or it can be usedto manipulate the sample. Again, when in a second position, or whentoggling between the first and second position, the probe 100 canmanipulate the surface of the sample 410. The controller 440 controlsoperation of the system 400 and probe 100. The system 400 can operate inany mode of scan probe imaging as described above.

FIG. 5 is an exemplary illustration of a probe or nanotweezer 500according to another embodiment. The probe 500 is similar to the probe100 and has similar characteristics which are interchangeable with thosedescribed above. In particular, the probe 500 can include a singlecantilever 540 and a tip or tweezers 510 mounted substantiallyperpendicular to the cantilever 540. The tip 510 can include a firstprong 520 and a second prong 530 mounted substantially perpendicular tothe cantilever. The cantilever 540 can be mounted to a base or siliconblock 590. Moreover, the cantilever 540 can include a first cantileverportion 550 and a second cantilever portion 560. The base 590 caninclude a silicon portion 592 integral with the cantilever and may alsoinclude a conductive or metal layer 594. The metal layer 594 can be usedto apply electrostatic force to actuate the prongs. The probe 500 andthe base 590 can be microfabricated in a batch process using siliconmicromachining technology discussed below.

In operation, the probe 500 can be used to image and manipulate asample. In particular, an electrical potential can be applied toportions of the metal layer 594 or the cantilever 540 to combine theprongs 520 and 530 to obtain an image of the surface of a sample.Additionally, the prongs 520 and 530 can be opened and closed byapplying appropriate voltages to the metal layer or to the cantilever540 to act as a nanomechanical tweezers. For example, a zero voltage canbe applied to open the tip 510 and non-zero voltage can be applied toclose the tip 510. Thus, the tip 510 can then be used to pick upparticles, replace particles, place particles, move particles, removeparticles, apply voltages, and perform other manipulations on a sample.

FIG. 6 is an exemplary illustration of a probe 600 according to anotherembodiment. The probe 600 is similar to the probes 100 and 500 and hassimilar characteristics which are interchangeable with those describedabove. In particular, the probe 600 can include a first cantileverportion 650, a second cantilever portion 660, and a first tip 620 and asecond tip 630 mounted substantially perpendicular to the cantileverportions 650 and 660. The cantilever portions 650 and 660 can be mountedto a base 690. The base 690 can include a silicon portion 692 and aconductive or metal layer 694.

In operation, the probe 600 can be used to image and manipulate asample. In particular, an electrical potential can be applied toportions of the metal layer 694 or the cantilever portions 650 and 660to combine the tips 620 and 630 to obtain an image of the surface of asample. Additionally, the tips 620 and 630 can be opened and closed byapplying appropriate voltages to the metal layer or to the cantileverportions 650 and 660 to act as a nanomechanical tweezers. For example, azero voltage can be applied to open the tips 620 and 630 and non-zerovoltage can be applied to close the tips 620 and 630. Thus, the tips 620and 630 can then be used to pick up particles, replace particles, placeparticles, move particles, remove particles, apply voltages, and performother manipulations on a sample.

FIGS. 7-20 are exemplary illustrations of a process for manufacturing aprobe according to one embodiment. For example, the process illustratedin FIGS. 7-20 can be implemented in a batch fabrication process tomanufacture many probes such as the probe 500 illustrated in FIG. 5. Thefigures are not necessarily to scale with respect to each other.

FIGS. 7-9 are exemplary illustrations of a cross-sectional view of asilicon wafer 700. FIG. 7 illustrates the silicon wafer 700 having afirst side of silicon nitride (Si₃N₄) 710 and a second side of siliconnitride 720. A photoresist pattern (not shown) can be created usingstandard lithography process (photoresist coating, pre-baking, maskexposure, post baking and developing). The photoresist pattern is usedas a mask to etch the uncovered silicon nitride in reactive plasma. Thephotoresist is then stripped away. The resulting structure containingtwo posts of silicon nitride 810 and 820 is shown in FIG. 8.

FIG. 9 illustrates silicon dioxide 900 thermally grown on a surface ofthe silicon 700 by using thermal oxidation of silicon process.Alternatively, the oxide can be deposited using a technique such asChemical Vapor Deposition. FIGS. 10 and 11 illustrate the formation of apost 1100 by lithography and silicon etching with a reactive plasmausing SiO₂ as a mask. FIGS. 12 and 13 illustrate the formation of prongs1310 and 1320 on the top of the post 1100 by lithography and etching thesilicon in reactive plasma using nitride as a mask. As shown in FIG. 12,the silicon dioxide is removed prior to the formation of the prongs 1310and 1320.

FIG. 14 is an illustration of plan view of a cantilever 1400 resultingfrom the above technique defined by lithography and subsequent etchingof the silicon nitride. The photoresist used can be very thick toprotect the prongs 1310 and 1320 and the posts 810 and 820 and to keepthem integrated with the cantilever. The cantilever 1400 includesintegrated prongs 1310 and 1320 from the above technique. FIG. 15 is anillustration of a cross-sectional view of the cantilever 1400 along lineA—A of FIG. 14.

FIG. 16 is an illustration of a silicon post 1600 used for additionalformation of the cantilever 1400. The wafer is then deposited withsilicon nitride for carrying out deep etching. A photoresist pattern isdefined on the backside of the wafer. The pattern is aligned withrespect to the cantilever on the front side. The nitride is then etchedwith reactive plasma from the backside using photoresist as the mask.The photoresist is then stripped and wafer is cleaned. The wafer is thenplaced in an anisotropic silicon etchant solution such as KOH. Thesilicon nidtride on the front side protects the structures from the KOH.The anisotropic etchant preferentially etches all crystal planes of thesilicon except the (111) plane. The etch rate of the (111) crystal planeis preferably very small.

FIG. 17 illustrates the structure when the etching is complete. FIG. 18illustrates the resulting structure after the silicon nitride layer ispreferably chemically etched. Thus, FIG. 18 illustrates a releasedcantilever 1400 with the integrated tips 1310 and 1320 (not shown). FIG.19 is an illustration of a cross-sectional view of the cantilever with alayer of insulating material 1910 and a layer of conductive material1920. The insulating material 1910 can be silicon dioxide, or the likeand the conductive material 1920 can be metal, or the like. FIG. 20 isan illustration of a plan view of the cantilever 1400 extending from abase 2010. Metal lines 1922 and 1924 are isolated from each other bycreating a gap 2020 using focused ion beam milling. The millingelectrically separates the tips 1310 and 1320 and creates contact pads1922 and 1924 on the substrate for supplying an electrostatic force foroperating the tips 1310 and 1320. Thus, the above process creates aprobe such as probe 500.

Many of the individual steps in the process described above can bealtered without affecting the utility of the final structure. Forexample one can use silicon-on-insulator wafer instead of single crystalsilicon wafer to have an etch stop and tighter control on the thicknessof the cantilever. The cantilever can be made from silicon dioxide orsilicon nitride. The length and thickness of the cantilever and theprongs can be varied. The process described above can be used for batchfabrication of several hundred probes on a single silicon wafer.

FIGS. 21-22 are exemplary illustrations of a probe system forimplementation of a focused ion beam milling technique for manufacturinga probe such as probe 100 according to another embodiment. FIG. 21 is anexemplary illustration of an existing probe 2100 that can be used inthis technique. The existing probe 2100 includes a tip 2110 and acantilever 2120 extending from a silicon base 2120. The probe isthermally oxidized. This step covers the entire probe with a silicondioxide layer. The tip side is then coated with a metal layer. FIG. 22is an illustration of a cross-sectional view along line A—A of the probe2100 illustrated in FIG. 21. As illustrated in FIG. 22, an insulatinglayer 2210 such as silicon dioxide is thermally grown or deposited onthe probe 2100 using oxidation techniques. Then, a conductive layer2220, such as metal is deposited over the oxidation layer 2210. The tip2110 can be milled to form prongs. The probe 2100 can then be milledalong the center of its length to electrically isolate the prongs. Themilling can also be performed into the silicon substrate 2130 to createpads for the application of voltages across the prongs. The resultingprobe such as the probe 100 or the probe 500 is illustrated in FIGS. 1or 5 respectively.

FIGS. 23-33 are exemplary illustrations of a process for manufacturingor microfabricating probe or nanotweezer 600 illustrated in FIG. 6according to another embodiment. The probe 600 includes the twocantilevers 650 and 660 which can be moved laterally with theapplication of an electrostatic force. Each tip 620 and 630 istriangularly shaped with a flat surface facing the other tip. Thus, thetips can close completely to grab tiny structures on or in a sample.

FIG. 23 is an exemplary illustration of a cross-sectional view of asilicon wafer 2300 having silicon nitride (Si₃N₄) 2310 and 2320 on bothsides. A photoresist pattern (not shown) is created on one side of thewafer. The resist pattern is used as a mask to allow the surroundingSi₃N₄ and silicon to be etched in a reactive plasma. FIG. 24 is anillustration of the formation of two silicon posts 2410 and 2420 on thesilicon wafer 2300 from the plasma etch. FIG. 25 is an illustration of aplan view of the silicon posts 2410 and 2420 on the silicon wafer 2300.Sharp corners 2510 and 2520 define the location of the desired tips,such as tips 120 and 130. FIG. 26 is an illustration of a crosssectional view of the silicon posts 2410 and 2420 and the silicon wafer2300 with silicon dioxide (SiO₂) grown on the surfaces without thesilicon nitride 2130 and the silicon nitride 2130 removed. Inparticular, the SiO₂ covers the entire surface of the wafer except forthe top of the posts 2410 and 2420 where the presence of the Si₃N₄prevents the growth of SiO₂. The Si₃N₄ is then selectively removed in areactive plasma.

FIG. 27 illustrates the wafer 2300 after it has been placed in ananisotropic silicon etchant such as KOH solution. Silicon is etched awayfrom the top of the new posts 2710-2740, but is not etched where theSiO₂ masks the silicon on the post sidewalls and the rest of the wafer2300 surface. Thus, the final profile of the etched out posts 2710-2740consist of triangular shaped features resting against the SiO₂ sidewallsat the corners of the posts 2710-2740. The length of the KOH etch istimed to produce the desired tip height. FIG. 28 is an illustration of aplan view of the remains of the etched-away posts 2710-2740. Thus, whenthe SiO₂ is subsequently removed, sharp tips, including tips 2710-2740,remain, pointing up substantially perpendicular from the surface of thewafer. At this step, multiple tips are formed whenever there are cornerson the original post pattern.

FIG. 29 is a cross-sectional view of the silicon wafer 2300 showing aninsulator 2910 and 2920, such as silicon dioxide or the like, placed onboth sides of the silicon wafer 2300. A conductive layer 2930, such as ametal layer or the like, is then placed on the top side of the siliconwafer 2300. FIG. 30 is an illustration of a pair of cantilever arms 3010and 3020 which are formed with the integrated tips 2710 and 2720. Thecantilever arms 3010 and 3020 can be formed by etching them out of theoxide layer 2910 and metal layer 2920 or by placing the tips 2710 and2720 onto existing cantilever arms 3010 and 3020.

FIGS. 31 and 32 are a cross-sectional view illustrating the release ofthe cantilevers 3010 and 3020 with integrated tips 2710 and 2720 byetching the silicon preferably with deep reactive ion etching process.For example, the cantilevers 3010 and 3020 and the tips 2710 and 2720are created by using a thick photoresist or mask to protect the desiredportions. The surrounding SiO₂ is then etched away. The mask is designedso that only the desired tips 2710 and 2720 are incorporated into thecantilevers 3010 and 3020 while the other tips, such as tips 2730 and2740 are sacrificed during the SiO₂ etch. FIG. 33 is a plan viewillustration of the resulting cantilevers 3010 and 3020 and the tips2710 and 2720. Many of the steps, material and shapes of the cantileverscan be altered without affecting the final structure. For example theeither or both of the cantilevers, a part or full, can have smallerwidth at the end that is attached with the substrate. Also, thecantilevers can be made out of silicon or silicon nitride.

FIG. 34 is an exemplary illustration of a user interface 3400 for usewith the probe 100. For example, the user interface 3400 is a graphicaluser interface (GUI) implemented on the controller 440 of FIG. 4. TheGUI is used for nanomanipulation and imaging of a sample wherenanomanipulation refers to the controlled positioning and analysis ofobjects typically at the molecular length scale which is about 1-100 nm.Such nanomanipulation can be applied to electronic devices, fundamentalmaterials science, biology, biotechnology, and other applications wherenanomanipulation is useful. In such applications an SPM is used toassemble particles in desired locations on a surface by nudging themwith a tip, by transporting them using switchable electrostatic forcesbetween the tip and the particle, and by picking up and droppingparticles using nanotweezers. The SPM is also used to cut singlemolecules, such as DNA, into well-defined segments using the tip at highforces, and then imaging the results nonperturbatively using low forces.The SPM is further used to facilitate construction and tests ofmolecular-scale devices such as nanotube-based transistors, or the like.The SPM is additionally used to measure electrical characteristics, suchas IV curves, at precise locations. The SPM is also used to measurecompliance and other mechanical properties of structures such asnanotubes, cells, or other nanoscale structures. The SPM is further usedto acquire data as the tip traces a user-defined path. The GUI can alsobe used with dip pens, nanotweezers, ion-conductance probes, opticalsensors, or the like. The GUI can further employ force feedback where auser can feel the tip encounter objects on the surface of a sample. TheGUI can be connected to closed-loop scanning hardware, for example, byusing reference voltages to determine lateral position. The GUI can alsobe connected to open-loop scanning hardware by using X-Y offsetvoltages. The GUI can also be used to employ the SPM to etch and scratcha sample or to move the SPM tip over the surface of a sample whileapplying a voltage to or across the sample.

The GUI 3400 can include a display screen or playing field that displaysan image 3402 received from the probe 100. The image 3402 can be fullsized or zoomed in. In addition, the image can be at a resolution of 512pixels or any other suitable resolution. Many actions can be enabled bydirect point-and-click events within this field. Colored cursors andlines can display tip position and path.

The GUI 3400 can also include a row of control/manipulation buttons 3404for tip movement, voltage control, and the like. The GUI 3400 canfurther include a row of scan/acquisition/display buttons 3406.Additionally, GUI 3400 can include a parameters box 3450 that displaysvalues of all parameters relevant to control of a probe such as tipvoltages, speed of tip moves, often adjusted feedback parameters, andthe like. The GUI 3400 can also include a status box 3470 that shows thestatus of several values of interest. Further, GUI 3400 can include adialog box 3480 that provides simple instructions for functionscurrently enabled. For example, the dialog box 3480 can provideinstructions for a move function as illustrated. The dialog box 3480 canalso show user alerts as appropriate, such as when a safety istriggered. The GUI 3400 can additionally include context icons 3490 thatcan take a user to other GUI's for 2-D scanning 3491, analysis 3494,force curves 3492, scopes 3493, and the like.

The control/manipulation buttons 3404 can include buttons 3410-3424. Themove tip button 3410 can perform basic tip positioning. A move tip modecan be enabled by clicking the move tip button 3410 once and disabled byclicking the button again or by enabling another function. When the movetip mode is enabled, a user can position a cursor at a desired locationwithin the field 3402. Clicking once can cause the tip to move to acursor position in a straight line with a velocity such as tip velocity3451. The path history of the tip can be drawn on the field 3402. Whenthe move tip mode is enabled, the dialog box 3480 can display: “Positioncursor at desired location and click. Tip will move to cursor position.”

The mop button 3412 can enable the tip to track a cursor in real time.When the mop mode is enabled, a user can click on any position in thefield 3402. The tip will then track the cursor in real time, with amaximum velocity set by the configure button 3448. Clicking the mopbutton 3412 once can enable this mode. The path history can be drawn ifdesired. Double clicking can stop the tracking. When the mop mode isenabled, the dialog box 3480 can display: “Position cursor at desiredlocation and click once; tip will track cursor. Double click to stop.”

The path button 3414 can enable the tip to follow a path of linesegments drawn on the field 3402. Clicking the path button 3414 once canenable the path mode. When the path mode is enabled, the user can clickon a series of positions on the field 3402 to draw a series of linesegments. Double clicking ends the series. The do it button 3444 can beused to cause the tip to trace the path of the line segments with aspeed set in tip velocity button 3451. The clear button 3446 can erasethe path and allow the GUI to wait for another path. The path historycan be drawn if desired. Double clicking can stop the tracking. When thepath mode is enabled, the dialog box 3480 can display: “Click at aseries of points to draw path. Double click to end path. Then select DoIt to move and Clear to erase path and redraw.”

The pulse voltage button 3416 can switch the tip voltage from a Ref V3452 voltage to a Pulse V 3453 voltage for a duration of Pulse Dur 3454as set in the parameters box 3450. When the pulse mode is enabled, afterthe first pulse, the dialog box 3480 can display: “Pulses tip voltageonce with each click.”

The switch voltage button 3418 can cause the tip voltage to be switchedfrom a current state to another state. For example, the tip voltage canswitch from the voltage defined in Ref V 3452 to the voltage defined inthe Pulse V 3453, the tip voltage can switch polarity, or the tipvoltage can switch to any other useful voltage. When the switch mode isenabled, the dialog box 3480 can display: “Switches tip voltage toopposite state.”

The lift tip button 3420 can act as a toggle. For example, the lift tipbutton 3420 can cause feeback to be turned off to the tip and the tiplifted to a height Δz 3455 by a z actuator such as a piezo. The servo onbutton 3421 is then enabled. The servo stays off until the button ispressed again. Pressing the servo on button 3421 can turn the feedbackon and cause the tip to seek the surface of the sample. This mode can beuseful for moving particles around the surface of the sample.

The reset z button 3422 can correct for z drift. This button can beenabled only when the feedback is off and the tip is lifted. The reset zbutton 3422 can cause feedback to temporarily seek a surface andredefine a tip/sample relationship. For example if a tip is inTappingMode™, tapping oscillation and feedback are turned on. Once thesurface is found, the feedback and drive oscillation are turned off. Thetip and sample separation is then equal to half the tip oscillationamplitude, which should be known in nm if the system sensitivity isappropriately calibrated. The z height is then adjusted to bring the tipback to lift Δz 3455. This mode can be accurate to, for example, about 2nm. If the tip is in contact mode, deflection can be used to trigger ina similar manner.

The run script button 3424 can open a file-pick box from which a usercan select, for example, a lithography script to run. During execution,tip motion is shown in the field 3402 and the path history can be drawnin the field 3402.

The scan/acquisition/display buttons 3406 can include buttons 3426-3440.The refresh field button 3426 can cause the entire field 3402 to bescanned with currently set scan parameters. Frame location and zoomingfunctions can be set using the configure button 3448. The refresh regionbutton 3428 can allow the user to define a region on the field 3402. Forexample, the user or the GUI can draw a box on the field 3402 defining aregion. The user can resize and reposition the box. By pressing the doit button 3444, the region within the box is rescanned. Thus new datacan replace old data in the box in the field 3402.

The survey button 3430 can cause the entire field 3402 to be coarselyrescanned using current scan parameters set using, for example, theconfigure button 3448. Also, the resolution of the survey rescan can beset in the survey pixel parameter 3460.

The zoom button 3432 can cause a box to be drawn on the field by theuser or by the GUI. The user can then size and locate the box to selecta region to be zoomed in. The GUI zooms in to the selected area when theuser presses the do it button 3444. The user can use the configurebutton 3448 to set the system to zoom in by rescanning the area or tozoom in on the area with data currently in the system.

The move field button 3434 can cause a cross cursor to be drawn in thecenter of the field 3402. The user can then click on the field 3402 tograb the cursor and move the center to a new position. Clicking againcan cause the cursor location to define the center of a new field 3402.Additional positioning and clicking can refine the positioning. The usercan then click the do it button 3444 to translate the image 3402accordingly. Newly exposed regions can be left blank until refreshed orcan be scanned upon translation.

The hide path button 3436 can cause the tip path to be displayed orhidden when the tip moves. The mode can default to show the path. Thepath can remain until the field 3402 or a region is refreshed or thebutton is pressed. The hide path button 3436 can then change to read“show path” when the path is hidden. Switching back to show the path canthen cause any subsequent tip paths to be shown.

The accent changes button 3438 can be used to highlight data that maydiffer from the most recent scan. For example, regions that aremanipulated can be highlighted until the manipulated regions arerescanned. This feature is not necessary when the image is scanned whilethe image is being manipulated.

The capture button 3439 can cause the current field to be captured and afile save box to open for saving the image. The stop button 3442 canstop any current action. The do it button 3444 can be enabled asappropriate for the functions described above. The clear button 3446 isalso enabled as appropriate for the functions described above. Forexample, a user can clear a drawn path by hitting the clear button 3446.

The configure button 3448 can open a menu for configuring parameters andoptions of the GUI. Features that can be configured include refreshpreferences, options to hide status boxes, zoom configuration, and zsafety configuration. The z safety configuration prevents damage to atip that can result from moving the tip into a sloping surface and tallobstacles. The z safety configuration also configures the system tomonitor if the tip drifts. For example, manipulation can be disabled andan alert shown when the tip drifts out of an acceptable range or when DCdeflections exceed a trigger. Parameters for z safety can includeon/off, z center range in volts relative to zero volts, and DC triggervoltage.

The parameters box 3450 can display values of the operation of the probein real time, if necessary. The values can be disabled if appropriate oroverridden by lithography scripts. Values can be changed by numericalentry, arrow keys/buttons, or any other suitable manner. Tip velocity3451 is in effect during lateral movement of the tip. Ref V 3452 is thedefault tip voltage. Pulse Voltage 3452 is the tip voltage applied whenthe voltage of the tip is pulsed using the pulse button 3416 or switchedwith the switch voltage button 3418. Pulse Dur 3454 sets the length of avoltage pulse when the pulse button 3416 is pressed. Lift Δz 3455 is fortip and surface spacing is enabled when feedback is off. This allows thetip to be lifted a desired distance above a surface or pushed into thesurface with negative values. This parameter is disabled when feedbackis on.

Servo Mode 3456 is for selecting TappingMode™ or contact mode. It isactive when feedback is on and can be switchable at all times. Setpoint3457 is in effect during lateral moves and scans and is enabled whenfeedback is on. Drive Amp 3458 is active when TappingMode™ is enabledand can be applied with feedback on or off. Pixels/Line 3459 is forsetting the data or pixel density in the field 3402. Survey Pixels 3460is for setting the pixel density used in a survey scan. Aspect Ratio3461, Scan Rate 3462, I Gain 3463, and P Gain 3464 all are forparameters as described.

The status box 3470 can display various useful system values 3471-3479that might not otherwise be shown. The values can be collected for easyreference. The status box 3470 can be hidden by using the configure box3448.

Referring to FIG. 35, a scanning probe microscope (SPM) 3500 is shown.The SPM 3500 can be used in conjunction with the probe 100. The SMP 3500includes a chassis including a support 3502 to which an actuatorassembly 3504 is attached. In addition, a sample base 3506 is fixed tosupport 3502 and is configured to accommodate a sample 3508. Theactuator assembly 3504 includes an actuator 3510, a reference assembly3511 comprising, among other structure, an elongate reference structure3512 that surrounds actuator 3510, and a probe assembly 3513.Preferably, reference structure 3512 is tubular and has a longitudinalaxis that is generally collinear with the longitudinal axis of actuator3510. Actuator 3510 can be piezoelectric or electrostrictive, and is atube actuator or another type of actuator conventional in the art ofnanopositioning systems.

At a lower free end 3505 of actuator assembly 3504, a probe assembly3513 is attached and includes a cantilever 3514 having a stylus 3515attached thereto. The cantilever 3514 and the stylus 3515 can comprisethe probe 100. During operation, stylus 3515 is scanned across thesurface of a sample 2508 to determine surface characteristics (e.g.,topography) of the sample. The scanning operation is provided byactuator 3510, which is driven by program-controlled signals (e.g.,appropriate voltages) to cause the actuator 3510 to move laterally intwo dimensions across the surface of sample 3508, as well as to extendand retract the probe assembly 3513, i.e., to move cantilever 3514toward or away from the sample, typically in response to closed loopsignals derived from sensor a 3509. As a result, the actuator 3510preferably can translate the cantilever 3514 in three orthogonaldirections under program control. Note that for convenience we willrefer to the extending and retracting of the probe assembly 3513 towardand away from sample 3508 as motion in the Z direction, and translationlaterally across the surface of the sample as motion in the X directionand the Y direction, where the X and the Y axes are orthogonal to eachother and define a plane substantially parallel to the surface of sample3508. This nomenclature is used purely for convenience to indicate threeorthogonal directions.

Referring to FIGS. 35 and 36A, an electromagnetic radiation source 3526(e.g., a laser) is fixed to support 3502. In operation, the source 3526directs light towards a lower portion 3505 of actuator assembly 3504,while detector 3528 receives light from the light source 3526 after ithas reflected off this lower portion 3505 so as to monitor the amount ofactuator movement. Electromagnetic radiation detector 3528 is fixedrelative to support 3502 as well, and is employed as part of a measuringdevice 3650 to determine the amount of translation of at least part ofthe actuator 3510.

With more specific reference to FIG. 36A, the source 3526 of measuringdevice 3650 may be mounted so as to direct a beam of light generallyvertically toward a mirror 3652 positioned to deflect the beam towardsthe lower portion 3505 of assembly 3504. Preferably, a focusing lens3654 is disposed between light source 3526 and mirror 3652. The beam isthen deflected toward a sensor 3528 (e.g., a position sensingphotodiode) via the mirror 3656. A cylindrical lens 3658 may be disposedbetween the mirror 3656 and the sensor 3528 (or can be located at anypoint between source 3526 and sensor 3528 as desired) to again enhanceprecision.

Still referring to FIGS. 35 and 36A, to monitor, for example,topographical changes on the surface of the sample and provideappropriate feedback depending on the mode of SPM operation, anelectromagnetic radiation source 3507 (shown in FIG. 35) is fixed tosupport 3502. Source 3507 generates radiation that is directed throughactuator 3510 towards a mirror 3517 supported by a surface of cantilever3514 of probe assembly 3513. Mirror 3517, in turn, directs the radiationtoward detector 3509 (shown in FIG. 35). Mirror 3517 may, in thealternative, be a polished portion of the back (upper) side of thecantilever 3514. The detector 3509 receives the light reflected from theprobe 3514 and, in turn, generates a signal indicative of, for example,the deflection of the probe 3514, as is conventional in the art.

The entire actuator assembly 3504 is shown in more detail in FIG. 36B.Actuator assembly 3504 includes actuator 3510 (preferably apiezoelectric tube) and reference assembly 3511 which in turn comprisesreference structure 3512, coupling mount 3628, flexible bar coupling3630, flexure 3632, and slotted disk 3650 as described in detail below.

In the preferred embodiment of the present invention, actuator 3510 isformed of two sections; first, an upper section 3620 that is configuredto deflect laterally in a plane lying perpendicular to the axis of theactuator under program control. For this reason it is termed an X-Ytube. Actuator 3510 also includes a lower Z tube actuator 3622 that isadapted to extend or retract in a direction substantially parallel tothe longitudinal axis of the tube under program control. A discussion ofa means for controlling such actuators can be found, for example, inU.S. Pat. No. 6,008,489 and other related applications.

Two tubes 3620, 3622 of the piezoelectric actuator 3510 are coupledtogether end-to-end proximate to a circular collar 3624 that extendsaround and is fixed to the actuator 3510. Assembly 3504 is preferablycoupled to frame 3502 of the scanning probe microscope with a flange3626 that is fixed to the top of X-Y tube 3620. In this preferredembodiment, tubular member or elongate reference structure 3512 ofreference assembly 3511 extends around at least the Z tube 3622 of theactuator 3510 and is fixed to collar 3624. Collar 3624, in turn, isfixed to the actuator 3510 at or near the junction of the upper andlower actuator sections. When X-Y tube 3620 is driven under programcontrol, it deflects in a direction generally perpendicular to thelongitudinal axis of actuator 3510. Since collar 3624 and hencestructure 3512 are fixed to the actuator near the bottom of X-Y tube3620, they also deflect laterally.

On the other hand, when Z tube 3622 is driven under program control itdoes not extend or retract collar 3624. Therefore, structure 3512 willnot extend or retract since it is coupled to collar 3624. When Z tube3622 extends or retracts, it extends or retracts relative to structure3512 which causes a substantial change in the relative position of thetwo at the lower (or free) end of Z tube 3622.

Semi-circular coupling mount 3628 is fixed to the lower end of Z tube3622 and translates together with Z tube 3622 when Z tube 3622 extendsand retracts. Reference assembly 3511 also includes a flexible barcoupling 3630 that, in turn, is fixed to coupling mount 3628. Bar 3630is configured so that when Z tube 3622 extends and retracts, the barcorrespondingly extends and retracts with respect to structure 3512.

In the preferred embodiment of the present invention, an opticalmeasuring apparatus 5010 measures movement of probe assembly 3513 in theX and/or Y directions (e.g., the XY plane) in response to voltagesignals applied to X-Y actuator 3620. Optical measuring apparatus 5010includes an objective 5012 fixed to reference structure 3512, a lightsource 5014, and a position sensor 5016. Movement of objective 5012depends on movement of reference structure 3512, while light source 5014and position sensor 5016 are stationary. Objective 5012 is locatedbetween light source 5014 and position sensor 5016.

In operation, flexible bar coupling 3630 and reference structure 3512provide a rigid mechanical connection in the XY plane between probeassembly 3513 and the bottom of X-Y actuator 3620, therefore minimizingany error introduced by Z tube 3622 in the XY plane as described above.Movement of reference structure 3512 is thus indicative of accuratemovement of probe assembly 3513 in the XY plane in response to voltagesignals applied to X-Y actuator 3620. Likewise, movement of objective5012 mounted to reference structure 3512 corresponds to movement ofprobe assembly 3513 in the XY plane.

Optical measuring apparatus 5010 provides optical magnification betweenlight source 5014 and position sensor 5016. In operation, X-Y actuatorassembly 3620 is actuated in response to voltage signals and moves in aparticular direction (e.g., in the X and/or Y directions), therebycausing reference structure 3512 and corresponding objective 5012 tomove. The position at which a beam of electromagnetic radiation fromlight source 5014 (e.g., a light beam) contacts position sensor 5016through objective 5012 is indicative of the movement of probe assembly3513 as position sensor 5016 and light source 5014 are both fixed. Inparticular, the magnification provided by objective 5012 is based on:M=1+i/o

where “i” is the orthogonal distance from the principal plane ofobjective 5012 to position sensor 5016, and “o” is the orthogonaldistance from the principal plane of objective 5012 to light source5014. Objective 5012 provides optical magnification to increase thesignal-to-noise ratio by multiplying the signal by a factor of M (e.g.,if M=5, for every micrometer that objective 5012 moves in the X and/or Ydirections, the light beam moves across position sensor 5016 by 5micrometers, thereby increasing the signal-to-noise ratio by a factor of5). Objective 5012 further comprises a set of separate microlenses(e.g., 3) that is fixed to an outside surface 5018 of referencestructure 3512 opposite an inside surface 5020 adjacent to Z tube 3622.

Position sensor 5016 is an XY position sensor (e.g., a siliconephotodiode) configured to detect the position of the light beam andgenerate a displacement signal indicative of movement of probe assembly3513 in response to voltage signals applied to X-Y actuator 3620 (e.g.,in a direction generally perpendicular to the longitudinal axis ofactuator 3552).

Turning to FIGS. 36C and 36D, alternate embodiments of the measuringdevice 5010 as illustrated in FIG. 36B are shown. In FIG. 36C, measuringdevice 5040 includes a light source 5044 that is fixed to referencestructure 3512, an objective 5042, and a position sensor 5046. In thiscase, movement of the light source 5044 depends on the movement of thereference structure 3512, while objective 5042 and position sensor 5046are stationary. Objective 5042 is located between light source 5044 andposition sensor 5046. In this embodiment the magnification of the lenspreferably equals,M=i/owhere “i” is the orthogonal distance between the principal plane ofobjective 5042 and the position sensor 5046, and “o” is the orthogonaldistance between the light source 5044 and the principal plane ofobjective 5042.

Turning to FIG. 36D, measuring device 5060 includes a light source 5064,an objective 5062, and a position sensor 5066 that is fixed to referencestructure 3512. In this case movement of the position sensor 5066depends on the movement of the reference structure 3512, while lightsource 5064 and objective 5062 are stationary. Objective 5062 is locatedbetween light source 5064 and position sensor 5066. In this embodimentthere is no magnification of the objective and therefore themagnification preferably equals,M=1

Referring again to FIG. 36A, the lower end of a flexible bar coupling3630 is fixed to the probe support assembly or flexure 3632 of referenceassembly 3511. Flexure 3632 is preferably formed out of a solid block ofmaterial, and comprises aluminum or a similarly light alloy. The flexure3632 is generally in the form of a movable bar assembly or four barlinkage. These links are identified in FIG. 36A as 3632A, 3632B, 3632Cand 3632D.

Flexible bar coupling 3630 is fixed to link 3632B of flexure 3632. Whenthe Z tube 3622 retracts in the direction marked “A,” for example, thebar 3630 translates with the free end of the Z tube 3622. Because the Ztube 3622 is retracting, the bar 3630 is pulled upwardly toward theupper end of the actuator. This causes the link 3632B to translateupwardly substantially the same distance that the end of the Z tube 3622translates upwardly.

The link 3632B is supported at flexible joints 3633 and 3634 to links3632A and 3632C, respectively. The links 3632A and 3632C are coupled tothe link 3632D at flexible joints or linkages 3636 and 3638,respectively. When the link 3632B is pulled upwardly (again in thedirection marked “A”) from a relaxed position as shown in phantom inFIG. 36A, links 3632A and 3632C are deflected upwardly at one end by thelink 3632B. The other end of the links 3632A and 3632C generally rotateabout joints 3636 and 3638 (also shown in phantom).

Links 3632A and 3632C are preferably of generally equal length and areparallel to each other. Similarly, the links 3632D and 3632B arepreferably of equal length and parallel to each other. The link 3632D isfixed to the lower end of the structure 3512. Because the structure 3512does not translate upwardly or downwardly when the Z tube 3622 movesupwardly or downwardly (due to its connection to a collar fixed on theactuator 110 above the Z tube 3622) any expansion or contraction of theZ tube 3622 upwardly or downwardly causes the four bar linkage offlexure 3632 to deflect about joints 3633, 3634, 3636 and 3638.Preferably, a thickness t₁ of each of the links is approximately 0.9 mm,while the thickness t₂ of each of the joints is approximately 0.08 mm.

Thus, when the four bar linkage made of the links 3632A-D is deflectedupwardly or downwardly, they form a parallelogram arrangement and thereis substantially no rotation of link 3632B, only translation. As aresult, the link 3632B is preferably constrained to simply translateupwardly or downwardly.

In operation, electromagnetic radiation from the source 3526 isreflected off a mirror 3640 of measuring device 3650, the mirror 3640being mounted on flexure 3632, particularly link 3632D. This light isreflected downwardly and is reflected again, this time off a mirror3642, which is also fixed to flexure 3632, particularly link 3632C. Thelight reflected off mirror 3642 then is directed towards the detector3528, which generates a signal indicative of the location at which thereflected light impinges upon the detector 3528. The signal provided bythe detector 3528 changes depending upon the degree of deflection of thefour bar linkage of flexure 3632.

More particularly, comparing the relaxed position of the flexure 3632 inFIG. 36A to the upwardly deflected position shown in phantom, it isclear that upward deflection of link 3632B causes link 3632C to rotateabout joint 3638. This in turn causes mirror 3642 to rotate about joint3638. This movement of the mirror 3642 causes the light beam to reflectoff the mirror 3642 at a different angle than when the beam is reflectedoff the mirror 242 when the flexure is in the relaxed position. As aresult, the beam moves to a position on the detector 3528 that isdisplaced from the initial location of the beam, as shown in phantom. Itis this change in the position of light impinging on detector 128 thatcauses a change in the signal generated by the detector 3528, and hence,provides an indication that link 3632B has translated upwardly ordownwardly with respect to the free end of structure 3512 to which link3632D is fixed.

Notably, mirrors 3640 and 3642 are preferably disposed with respect toeach other such that the light sensed by detector 3528 is substantiallyimmune to lateral deflections of the member 3512. In the embodimentshown in the figures, there are several structural elements thatindividually and collectively contribute to this immunity. Inparticular, the mirrors 3640 and 3642 are disposed to return light tothe detector 3528 in a path substantially parallel to the path of thelight impinging upon mirror 3640 of the measuring device 3650, and thusform what is akin to a corner cube retro-reflector. As the Z tube 3622moves, the mirrors 3640 and 3642 maintain their general orthogonalrelationship, albeit in displaced fashion, thus affording accuratemeasurements of Z displacement. Another feature that contributes to thisaccuracy is the fact that the path of light impinging upon the mirror3640 and the path of light reflected from the mirror 3642 aresubstantially parallel to the surface of the sample (108 in FIG. 35).

When the structure 3512 is deflected laterally across the surface of thesample, by activation of a X-Y tube, for example, mirrors 3640 and 3642are also deflected. This occurs whether or not there has been any upwardor downward motion of Z tube 3622 with respect to the member 3512. Dueto the arrangement of the incoming and outgoing beams from mirrors 3640and 3642 and the orientation of those mirrors with respect to eachother, any lateral deflection will not substantially change the signalimpinging on detector 3528, and detector 3528 will continue to generatea signal indicative of the height of the flexure 3632 (and particularlylink 3632B), and therefore the probe above the sample generally withouterror.

The above-described apparatus is thus used to isolate the movement of Ztube 3622 in its intended Z direction, yet permit free lateral motion ofthe lower end 3505 of the actuator assembly 3504. At the lower end ofthe actuator assembly 3504, reference assembly 3511 includes a slotteddisk 3650 having four mounting pins 3652 (two shown), the slotted disk3650 being fixed to the lower portion of link 3632B. Next, the probeassembly 3513 includes a probe base 3501 (shown in FIG. 36A in phantomlines) that can be plugged or unplugged from the pins 3652 to hold theprobe base 3501 onto the slotted disk 3650. Probe assembly 3513 alsoincludes cantilever 3514 fixed on one end to the probe base 3501, and astylus 3515 attached to the free end of cantilever 3514.

The light source 3507 generates light that travels down through theactuator 3510, and is reflected off mirror 3517 and returns to detector3509. Whenever the cantilever 3514 is flexed upwardly or downwardlyabout its mounting point, mirror 3517 rotates about the fixed end ofcantilever 3514 and causes the light generated by source 3507 to movewith respect to detector 3509. This movement, in turn, causes a changein the signal generated by detector 3509 that indicates a change in theamplitude of the deflection of cantilever 3514, and hence a change inthe force and/or distance relationship of the probe assembly 3513 andthe sample surface 3508.

Typically, to determine the height of various features at differentlocations on the sample surface, probe assembly 3513 is moved laterallyacross the surface of the sample 3508. In operation, to direct the probelaterally, an electrical signal is applied to an X-Y tube, which in turncauses the lower portion 3505 of the actuator assembly 3504 to deflectin relation to the sample 3508. Depending upon the signals applied tothe X-Y tube, this can cause the probe assembly 3513 to move in twoorthogonal directions across the surface of the sample.

In one mode of operation, the stylus 3515 is in contact with the sample,and slight deflections of the cantilever 3514 caused by its moving overthe sample are measured. This is called “contact” mode. As the stylus3515 is deflected upwards, it moves cantilever 3514 and mirror 3517.This change in the position of mirror 3517 causes the reflected light tomove across detector 3509. The output of the detector 3509 is fed backto the Z tube 3622. Thus, flexing of the cantilever 3514 is a functionof the signal provided by detector 3509. In typical operation, theamount of flexing of cantilever 3514 is maintained constant by extendingor retracting Z tube 3622 (e.g., lengthening or shortening) in responseto a signal based on the output of the detector 3509. When the stylus3515 reaches a surface asperity that causes the cantilever 3514 to flexupward, therefore deflecting light with respect to detector 3509, theSPM 3500 attempts to restore the cantilever 3514 to the same position onor above the surface of the sample. This capability is provided by thedata acquisition and control module 3702 shown in FIG. 37 that extendsor retracts Z tube 3622 in order to restore cantilever 3514 to itsoriginal deflection.

In TappingMode™ operation, an oscillator (not shown) causes the free endof cantilever 3514 to oscillate up-and-down, typically at or near itsresonant frequency. As probe assembly 3513 approaches the surface of thesample, interaction between the surface 3508 and the stylus 3515 causesthe amplitude (or phase) of these oscillations to change. The angle ofthe radiation reflected from mirror 3517 changes in amplitudeaccordingly and causes a change in the location of the reflected lightincident upon detector 3509. Detector 3509, in turn, generates a signalindicative of the changed amplitude and provides this signal to thecontrol circuitry 3700 shown in detail in FIG. 37. The control circuitry3700 in turn provides a control signal to Z tube 3622 to adjust itslength to move the stylus 3515 up or down until the cantilever 3514returns to the desired oscillation amplitude. The control signal is thusindicative of surface features of the sample 3508.

Referring still to FIG. 37, a control circuit 3700 is shown connected tosections 3620 and 3622 of an actuator 3510 such as a piezoelectric tubeactuator, detectors 3528 and 3509, and sources 3526 and 3507. Controlcircuit 3700 includes data acquisition and control module 3702 which iscoupled to and drives actuator drivers 3704 and source drivers 3706.Actuator drivers 3704 are in turn coupled to tube actuators 3620 and3622 of actuator 3510. These drivers 3704 generate high voltage signalsnecessary to cause a X-Y tube to move laterally and Z tube 3622 toexpand and contract vertically. Source drivers 3706 are coupled to anddrive radiation sources 3526 and 3507. Control module 3702 is alsocoupled to and receives signals from detector signal conditioner 3708.Signal conditioner 3708 receives the raw signals from the two radiationdetectors 3528, 3509 and converts them into signals that can be read bycontrol module 3702.

Control module 3702 includes a series of instructions that controls theoperation of control circuit 3700 and hence, the operation of actuator3510. This includes instructions that receive and process signalstransmitted from detector signal conditioners 3708 that are indicativeof the radiation falling on detectors 3509 and 3528. The instructionsalso include instructions that transmit appropriate signals to actuatordrivers 3704 causing actuator drivers 3704 to generate the appropriatehigh voltage signals to tubes 3620 and 3622 of actuator 3510. Controlmodule 3702 also includes instructions to generate signals and transmitthem to source drivers 3706 causing source drivers 3706 to properlycontrol the radiation emitted by sources 3507 and 3526.

Control module 3702 monitors changes in the signal generated by detector3509 and determines, based upon changes in the signal, that thecantilever 3514 has been deflected, either upwardly or downwardly incontact mode, or that its amplitude of oscillation, in TappingMode™, hasincreased or decreased. In response to this signal, the control module3702 attempts to raise or lower the probe assembly 3513 until the signalgenerated by detector 3509 returns to its original level. To do this,the control module 3702 generates a signal and applies it to Z tube 3622of the piezoelectric tube actuator 3510, which in turn causes it tocontract or expand depending on the signal. This contraction orexpansion pulls flexible bar coupling 3630 upwardly or downwardly, whichin turn pulls link 3632B upwardly or pushes it downwardly, respectively.Link 3632B is mechanically coupled to the fixed end of cantilever 3514causing it to move with bar 3630. This motion of the fixed end ofcantilever 3514 causes mirror 3517 to be restored to its originalorientation, and hence, causes the light falling on detector 3509 togenerate its original signal levels. These restored signal levels aresensed by control module 3702 that then stops changing the signalapplied to Z tube 3622. In summary, the height information isinterpreted from the voltage fed to the Z tube 3622. Specifically, thevoltage fed to the Z tube 3622 as part of the usual feedback process ofmaintaining constant cantilever amplitude or deflection is also read bythe data acquisition and control module 3702 as an indication of sampleasperity height.

In accordance with the novel principles of the present invention,accurate Z height information is independently derived from detector3528 while the usual feedback process described above continues.Specifically, the control module 3702 uses the signal provided bydetector 3528 to determine the height of probe assembly 3513 in thefollowing manner. Again, we will assume that the stylus 3515 is beingtranslated across the surface of sample 3508 and reaches an asperity. Asin the previous case, this will flex cantilever 3514 upwardly in contactmode or reduce the amplitude of oscillation of the cantilever 3514 inTappingMode™ and cause the signal to change at detector 3509. Again, thecontroller 3702 will cause section 3622 to contract by changing thesignal applied to it. This, in turn, causes flexure 3632 to moveupwardly. As shown in FIG. 36A, this upward motion causes mirror 3642 todeflect downwardly and outwardly away from mirror 3640 and causes thelight generated by source 3526 to fall on a different portion ofdetector 3528. The signal that falls on detector 3528 is a function ofthe height of flexure 3632, and hence the height of the fixed end ofcantilever 3514. In this case, therefore, controller module 3702 readsthe signal generated by detector 3528 and determines the height offlexure 3632 (and hence, probe assembly 3513) directly.

The preferred embodiment also avoids another positional error due tolateral deflection of Z tube 3622 when it contracts or expands. It isimportant in most measuring processes to determine not only the heightof the surface of sample 3508, but also the location at which thatheight measurement occurred. The Z tube 3622 can undesirably deflectlaterally when it contracts or expands. Without reference structure3512, this would cause the probe to steer slightly forward, backward, tothe left, or to the right across the surface of the sample, rather thanmoving straight upwardly or downwardly. Link 3632B, which translatesupwardly and downwardly together with flexure 3632 and the probe itself,is isolated from these lateral deflections of Z tube 3622. Itcommunicates only the expansion and contraction of Z tube 3622 to theprobe.

The four bar linkage of flexure 3632 ensures that the probe itself canonly translate upwardly and downwardly with respect to member 3512. Itis flexible bar coupling 3630 that absorbs this lateral motion andprevents it from being communicated to probe assembly 3513 when Z tube3622 expands or contracts. Flexible bar coupling 3630 has sufficientflexibility that it can deflect slightly from side to side throughoutits length. It is provided with a length sufficient to permit theselateral deflections of the coupling 3630 to occur without introducingsignificant errors into the system. In this manner, member 3512 isisolated from longitudinal motion of the piezoelectric actuator 3510,but will communicate (X,Y) plane motions to flexure 3632. Flexible barcoupling 3630, flexure 3632 and particularly link 3632B are isolatedfrom lateral movement generated by the expansion and contraction of Ztube 3622, yet substantially duplicate the upward and downward motion ofZ tube 3622 and transmit it to probe assembly 3513. Thus, flexure 3632can provide for accurate positioning of a probe 100 such as ananomechanical tweezers.

Thus, this embodiment provides an assembly including an actuator 3504with a longitudinal axis having a fixed end, and a free end configuredto translate in at least one direction with respect to the fixed end, amultiple bar linkage having first and second links mutually constrainedto translate with respect to each other, and wherein the first link isfixed to a reference structure and the second link is constrained totranslate in a direction generally parallel to the longitudinal axis ofthe actuator, a coupling having first and second ends, the first endbeing fixed to the actuator proximate to its free end, and the secondend being fixed to the second link, the coupling adapted to transmitdisplacement in a direction substantially parallel to the longitudinalaxis of the actuator, an objective fixed to the reference structure,wherein the objective is between a light source and a position sensor,and the position sensor measures displacement of the objective in atleast one direction generally perpendicular to the longitudinal axis ofthe actuator, and a probe coupled to the actuator, wherein the probe isconfigured to manipulate the surface of a sample. The light source andthe position sensor can be stationary. The objective can include a setof microlenses. The set of microlenses can provide optical magnificationto increase a signal-to-noise ratio. The magnification can be M=1+i/owhere i is an orthogonal distance from the principal plane of the set ofmicrolenses to the position sensor and o is an orthogonal distance fromthe principal plane of the set of microlenses to the light source.Movement of a beam of electromagnetic radiation from the light sourcedirected to the position sensor through the set of microlenses can bemultiplied by a factor of M. The assembly can be a scanning probemicroscope. Also, the actuator can be a piezoelectric orelectrostrictive actuator. The probe can include a cantilever, a firsttip mounted on the cantilever, and a second tip mounted on thecantilever, the first and the second tip being configured to combine toform an imaging tip. A voltage can be applied across the first tip andthe second tip to combine the first tip and the second tip to form animaging tip.

FIG. 38 is an exemplary flowchart 3800 outlining the operation ofswitching from a deflection mode such as contact mode to an amplitudemode such as TappingMode™ for operating the probe 100 in a probe system400 according to a preferred embodiment. The flowchart 3800 can beimplemented by, for example, the controller 440 illustrated in FIG. 4.Prior to employing the flowchart 3800, the probe 100 can be scanning asample 410 in contact mode. The flowchart begins at step 3805, forexample, in response to a macro script or in response to a userselecting a function on a GUI such as GUI 3400. In step 3810, thecontroller 440 turns off the feedback of the probe system 400. In step3815, the controller 440 then lifts the tip(s) of the probe 100 off thesurface of the sample 410.

In step 3820, the controller 440 determines the change in deflection,ΔD, of the cantilever of the probe 100. In particular, the controller440 subtracts the free air deflection the probe 100 encounters off ofthe sample 410 with the deflection setpoint, which is the deflection setfor the probe 100 to encounter on the sample 410 when in contact modebased on, for example, an amount of force between the tip and sampleselected by the user. In step 3825, the controller 440 determines if theoscillation drive signal for the probe 100 is off. If the drive signalis off, the controller 440 turns the signal on in step 3830. Typically,the oscillation drive signal will be off when the probe is in contactmode. In step 3835, the controller 440 changes the feedback input foramplitude mode (TappingMode™) operation. In step 3840, the controllerresets the amplitude setpoint based on a percentage of the amplitude ofprobe oscillation and resets the gain values for proper amplitude modeoperation. In step 3850, the controller 440 turns the feedback back on.In step 3850, the process ends and the probe 100 is now in amplitudemode operation.

FIG. 39 is an exemplary flowchart 3900 outlining the operation ofswitching from an amplitude mode such as TappingMode™ to a deflectionmode such as contact mode for the probe 100 in a probe system 400according to a preferred embodiment. The flowchart 3900 can beimplemented by, for example, the controller 440 illustrated in FIG. 4.Prior to employing the flowchart 3900, the probe 100 can be scanning asample 410 in amplitude mode. The flowchart begins at step 3910, forexample, in response to a macro script or in response to a userselecting a function on a GUI such as GUI 3400. In step 3920, thecontroller 440 turns off the feedback of the probe system 400. In step3930, the controller 44 determines whether the oscillation drive signalwill be kept on after the probe 100 is switched to contact mode.Typically the oscillation drive signal will not be used in contact mode,and therefore the controller 440 turns off the drive signal in step3940. In step 3950, the controller 440 changes the input for feedback todeflection mode. In step 3960, the controller 440 determines the freeair deflection of the probe 100. In step 3970, the controller 440determines the deflection setpoint for contact mode. In particular, thecontroller 440 calculates the deflection setpoint by adding the changein deflection AD calculated, for example, in accordance with step 3820of method 3800 to the free air deflection determined in step 3960. Instep 3980, the controller 440 turns on the feedback. In step 3990, theprocess ends and the probe 100 is now in contact mode operation.

Turning next to FIGS. 40 and 41, an alternative method for forming ananomanipulation tip 4002 according to the present invention is shown.In FIG. 40, apparatus 4000 for forming tip 4002 includes a millingsource 4004, such as a focused ion beam source, that generates a beam“B” that initially is directed toward a, for example, conventional SPMtip 4006 made of a material such as silicon. To produce tip 4002 (FIG.41), the method initially includes creating an opening 4008 in tip 4006with beam B of an appropriate dose. Beam B is translated toward a freeend 4010 of tip 4006 to create a narrow opening 4012 and tip 4006, thusforming two “arms” 4014, 4016 having generally opposed faces 4018, 4020,respectively. The forming of narrow opening 4012 may be effectuated byrotating ion beam source 4004 in a direction labeled “C” in FIG. 40 sothat beam “B” moves along the length of tip 4006 (illustrated bysequential beams “B′” and “B″” shown in phantom) and through the apex ata selected rate so opening 4012 is configured as shown in FIG. 41. Othermethods could be used, such as translating the SPM tip 4006 relative tothe beam, or moving the entire source 4004 along the length of the tip.

Notably, opening 4008 is formed sufficiently large so that “weak” orflexure points 4022, 4024 are created. Flexure points 4022, 4024 allowtranslation (e.g., rotation) of arms 4014, 4016 so that at least aportion of faces 4018, 4020 can be brought into contact with oneanother. As a result, nanomanipulation tip 4002 can be used to bothimage and manipulate nanoscale objects, as described above. In thisregard, electrodes (not shown) are placed on arms 4014, 4016 (preferablyadjacent free end 4010 of tip) to allow actuation thereof withappropriately applied voltages, again as described above. An SEMphotograph of the probe fabricated using this technique is shown in FIG.44. It may be noted that the figure shows only the apex of the tip thathas been milled.

FIG. 42 is an exemplary illustration of plan view of a probe system 4200according to an alternate embodiment. The probe system 4200 includes afirst probe assembly 4210 and a second probe assembly 4220. The firstprobe assembly 4210 includes a tip 4211, a cantilever 4212, a probeactuator 4213, and contacts 4214 and 4215. The second probe assembly4220 includes a tip 4221, a cantilever 4222, a probe actuator 4223, andcontacts 4224 and 4225. The probes assembly 4210 and assembly 4220 canextend from the same silicon base 4250. The probe system 4200 alsoincludes metal pads 4241-4244 and metal lines 4231-4234. The probesystem 4200 can be manufactured by a lithographic and etching processsimilar to the one disclosed above with respect to other probes.

In operation, one tip 4211 can be used to image a sample and the othertip 4221 can be used to manipulate a sample. In particular, one tip canbe raised, for example, by applying a voltage to metal pads 4241 and4242. This voltage can then actuate the actuator 4213 through thecontacts 4214 and 4215. The actuator 4213 can be a thermal actuator, apiezoelectric actuator, or any device that can be useful for adjusting aposition of the probe assembly 4210. The actuator 4213 can then raisethe probe assembly 4210 from the surface of a sample so that the otherprobe assembly 4220 is in contact with the sample for imaging or formanipulation. Alternately, the actuator 4213 can lower the probeassembly 4210 so that it is in contact with the sample for imaging ormanipulation. This can provide for one imaging probe and onemanipulation probe in close proximity. For example, the probes can beless than 20 microns apart. Preferably, the probes are less than 10microns apart or are even less than 5 microns apart. According toanother embodiment, one probe may include an actuator and one probe doesnot. According to the illustrated embodiment, one probe can be adjustedin one direction and the other probe can be adjusted in the otherdirection for alternating between imagine and manipulation. Thus, thisembodiment provides for positioning and removal of one probe on thesurface for imaging and the positioning and removal of another probe onthe surface for manipulation. Additionally, only one probe may be on thesurface at a time.

FIG. 43 is an exemplary illustration of a probe system 4300 according toan alternate embodiment. The probe system 4300 can include probes 4310and 4320. The probe 4310 can include a tip 4311 and a cantilever 4312.The probe 4320 can include a tip 4321 and a cantilever 4322. The probes4310 and 4320 can extend from the same silicon base 4340. The probesystem 4300 can also include metal layers 4313 and 4314. The probesystem 4300 can further include an oxide layer 4360 formed as a resultof an etching process similar to the one disclosed above and used toform the probes 4310 and 4320.

In operation, one probe is used to image the surface and another probeis used to manipulate the surface. A differential voltage can be appliedbetween the metal layers 4313 and 4314 to adjust a position of theprobes 4310 and 4320. Alternately, the probes can be adjusted usingpiezoelectric actuators, using thermal actuators, or using any othermethod for adjusting the position of the probes 4310 and 4320. Thus, oneprobe can be removed from a sample when the other is used to image thesample. Then, the other probe can be removed from the sample while theone probe is used to manipulate the sample. Thus this embodiment alsoprovides for one imaging probe and one manipulation probe in closeproximity. For example, the probes can be less than 20 microns apart.Preferably, the probes are less than 10 microns apart or are even lessthan 5 microns apart. This embodiment also employs similar features tothe other disclosed probe embodiments.

Thus, the embodiments disclosed in FIGS. 42 and 43 provide a scanningprobe microscope for imaging and manipulating a sample that includes afirst tip, a second tip, and an actuator coupled to the first tip, theactuator being configured to adjust the position of the first tip to afirst position for imaging the sample with the scanning probe microscopeand to adjust the position of the first tip to a second position formanipulating the sample with the scanning probe microscope. The scanningprobe microscope can also include a base, wherein the first tip iscoupled to the base and the second tip is coupled to the base. The firsttip can be an imaging tip, the second tip can be a manipulation tip, andthe actuator can be configured to adjust the position of the imaging tipto an imaging position for imaging the sample with the imaging tip andthe actuator is configured to adjust the position of the imaging tipaway from the sample for manipulating the sample with the manipulationtip. Alternatively, the first tip can be a manipulation tip, the secondtip can be an imaging tip, and the actuator can be configured to adjustthe position of the manipulation tip to a manipulation position formanipulating the sample with the manipulation tip and the actuator isconfigured to adjust the position of the manipulation tip away from thesample for imaging the sample with the imaging tip. The actuator canadjust the position of the first tip in response to at least one of avoltage differential applied to the actuator and a thermal differentialapplied to the actuator. Accordingly, using one probe for imaging andanother probe for manipulation can reduce or eliminate the contaminationof the imaging probe from manipulation.

While this invention has been described with specific embodimentsthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art. For example,various features of the embodiments are interchangeable with varioussimilar features of other disclosed embodiments. Thus, all of thefeatures disclosed with respect to each embodiment can be applied to theother embodiments to achieve desirable results. Accordingly, thepreferred embodiments of the invention as set forth herein are intendedto be illustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the invention.

1. A method for operating a probe that interacts with a surface of asample, comprising: scanning a region the surface of the sample with theprobe; manipulating the surface of the sample with the probe; selectinga subregion of the region; and rescanning the selected subregion of theregion of the surface of the sample.
 2. The method for operating a probethat interacts with a surface of a sample according to claim 1, whereinthe manipulating step further comprises manipulating the surface of thesample with a probe other than the probe used to scan the region of thesurface of the sample.
 3. The method for operating a probe thatinteracts with a surface of a sample according to claim 1, wherein themanipulating step further comprises manipulating the surface of thesample with the probe used to scan the region of the surface of thesample.
 4. The method for operating a probe that interacts with asurface of a sample according to claim 3, wherein the manipulating stepfurther comprises manipulating a subregion of the region of the surfaceof the sample with the probe, and the rescanning step further comprisesrescanning the manipulated subregion of the region of the surface of thesample.
 5. The method for operating a probe that interacts with asurface of a sample according to claim 3, wherein the manipulating stepfurther comprises manipulating particles on the surface of the samplewith the probe.
 6. The method for operating a probe that interacts witha surface of a sample according to claim 3, wherein the manipulatingstep further comprises manipulating particles on the surface of thesample by picking up the particles with the probe.
 7. The method foroperating a probe that interacts with a surface of a sample according toclaim 1, wherein the probe comprises: a cantilever; a first tip mountedon the cantilever; and a second tip mounted on the cantilever, the firstand the second tip being configured to combine to form an imaging tip.8. The method for operating a probe that interacts with a surface of asample according to claim 7, further comprising applying a voltageacross the first tip and the second tip to combine the first tip and thesecond tip to form an imaging tip.
 9. A method for operating a probethat interacts with a surface of a sample, comprising: scanning a regionof the surface of the sample with the probe; manipulating the samplewith the probe; rescanning a subregion of the region of the surface ofthe sample; and applying a voltage across the first tip and the secondtip to combine the first tip and the second tip to form an imagingprobe, wherein the probe comprises: a cantilever; a first tip mounted ona cantilever; and a second tip mounted on the cantilever, the first andthe second tips being configured to combine to form an imaging probe.